SQL Server Management Studio says:
Msg 8120, Level 16, State 1, Procedure udForumTopicMessageByForumTopicID, Line 6
Column 'T_ForumTopicMessage.ForumTopicMessageID' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

I'd like to get beyond this, just to find out if the join on itself will
even work.
Or maybe someone has a better way to do this?